Electronic switches, such as MOSFETs, IGBTs, or other types of transistors are widely used as electronic switches for switching electrical loads, such as motors, lamps, magnetic valves, and the like. In these applications, the electronic switch is connected in series with the load, where the series circuit with the electronic switch and the load is connected between power supply terminals. The load can be switched on and off by switching the electronic switch on and off.
Usually, the on-resistance of the electronic switch, which is the resistance of the electronic switch in the on-state, is lower than the resistance of the load, so that in a normal operation state a voltage drop across the electronic switch is significantly lower than a voltage drop across the load, when the electronic switch is switched on. When, however, there is a short circuit in the load and when the electronic switch is in the on-state, the voltage drop across the electronic switch increases and the electric power dissipated in the electronic switch increases. The increase in dissipated power results in an increased temperature of the electronic switch.
Also, during normal operation without a short circuit in the load, high current applications increase the electric power dissipated in the electronic switch, causing the temperature of the electronic switch to increase. Rising ambient temperature may also increase the junction temperature of the electronic switch. Regardless of whether the temperature increase indicates a short circuit problem, is due to normal high-current operation, or is caused by higher ambient temperature, too much temperature increase may lead to device failure or destruction in some cases or to nonoptimal performance in other cases. In order to prevent reduced performance or failure, the temperature in the electronic switch may be detected and the electronic switch may be switched off when the temperature reaches a given temperature threshold.
In order to detect the temperature in the electronic switch, a temperature measurement device may be included with the electronic switch inside the same package or attached to the package containing the electronic switch. The temperature measurement device includes a temperature sensor that indirectly measures the temperature of the electronic switch.